The present invention relates to an improved mold apparatus and method for producing encapsulated glass. More particularly, the invention relates to a mold apparatus and method for producing an encapsulated window assembly including a glass sheet and a gasket of a polymeric material which is formed to encapsulate the peripheral edge of the sheet. Typically, the gasket is formed by a reaction injection molding process.
Conventional window assemblies for automobiles have been provided with a number of different elements. The bedding, or embedding or encapsulating, of glass window sheets into metal frames so as to form assemblies to be subsequently attached to an automobile body, has been done in the past by manual assembly techniques. Such manual techniques included inserting a window glass sheet into a frame, then covering the edge of the glass sheet with a strip of rubber, which was inserted into the metal frame holding the glass sheet. The edges of the rubber strip extending out of the frame were trimmed off by the use of a hot knife. This process was expensive due to the fairly high cost of the labor involved. Other problems arose as well, such as the costs of the additional step of cleaning or washing the window assembly and the inability of the window assemblies so formed to withstand the weather. As a result of such disadvantages, techniques for automatically bedding the glass sheets into such a frame have been developed. An example of such a method and apparatus is described in U.S. Pat. No. 3,263,014, which is incorporated herein by reference.
Early window assemblies often included a number of different elements, including adhesive sealants applied around the peripheral edges of the glass sheet, suitable mechanical fasteners such as metal clips, and exterior trim pieces. Subsequent window assemblies were developed in attempts to further improve on the earlier window assemblies. An illustration of a more recent window assembly is provided in U.S. Pat. No. 4,072,340, which is incorporated herein by reference. The window assembly disclosed in this latter patent includes a glass sheet, a frame, fasteners for affixing the assembly to a vehicle, and a casing or gasket of a molded material extending between the frame and the edge of the glass sheet. The purpose of such a gasket is to hold the glass sheet and the frame together.
In connection with the manufacture of window gasket assemblies of the more recent design, a mold apparatus is used. The mold typically used includes two mold sections which define a chamber for receiving the sheet. Such molds also include a gasket forming cavity formed by the cooperation of the mold sections, the sheet (around the peripheral edge of which a gasket is to be formed), and one or more seals positioned within the mold sections. A smooth and polished finish on any exposed surface, usually the exterior facing surface of the window gasket assembly as it is to be installed in an automobile window opening, is desired for aesthetic reasons. It is therefore desirable to have the facing surface of the mold section which defines an exposed or exterior surface of the window gasket assembly finished or polished so as to provide a smooth and finished surface of the gasket assembly. However, it is undesirable for the mold sections to come into contact with the glass sheet. Such contact often results in excessive fracturing or scratching of the glass sheet. Thus, a chamber in which the glass sheet is to be positioned is often formed in the interior of the mold so that the sheet, around the periphery of which an encapsulating gasket is to be formed, is not in contact with the mold sections.
A seal is conventionally provided within the mold to prevent the gasket forming material from leaving the gasket forming cavity. Even with such a seal, the leakage of the gasket forming material onto the sheet to form a layer of flash is common in conventional molds. In the past, this problem has been addressed by allowing for a flashing space defined by a seal, the glass sheet, the mold section with the facing surface, and the gasket forming cavity. During the molding process, some of the material being molded as a gasket enters the flashing space from the gasket forming cavity and cures on the glass sheet. An example of such a prior art mold apparatus and method is illustrated in U.S. Pat. No. 4,688,752, which is incorporated herein by reference. The production of such flash on the glass sheet, however, is undesirable as the flash is usually removed for aesthetic reasons prior to the installation of the window assembly on an automobile body. The added step of removing the flash creates additional labor costs and waste.
The glass sheets used in the manufacture of window gasket assemblies (or "unitary" assemblies) are typically produced with irregularities in the surface. Additionally, the glass sheets used in manufacturing such assemblies often have a curved configuration by design. Such curved configurations also produce difficulties in connection with a lack of uniformity among and the tolerances for curved sheets with respect to the dimensions of the sheets. Prior art mold sections used in manufacturing such assemblies have been made of steel or other metals. In the manufacturing process, the mold sections are brought together when the mold is closed; in some instances, the mold sections may be clamped together at a relatively high pressure. Since the steel surfaces of the mold sections do not yield or conform to irregularities in the surface of the glass sheet, the glass sheet may be fractured or scratched by the mold sections. Additionally, the glass sheet may be scratched during the steps of inserting and removing the glass sheets into and from the mold sections if the glass sheet slips. The breakage or scratching of a glass sheet renders the glass sheet useless as a window assembly and thus results in extra costs. Other disadvantages of such metallic mold sections are the costs of the mold sections themselves and also the amount of time and effort needed to make and modify such mold sections.